The present invention relates generally circuits and methods for operating isolated buck converters to maintain continuous current mode operation. More particularly, the present invention pertains to maintaining continuous current mode operation in a buck converter while protecting inverter switches during non-zero voltage switching.
Operating an isolated buck converter at low output levels (i.e., low output current) can cause an output inductor of the isolated buck converter to operate in a discontinuous current mode. This places additional burden on an output capacitor of the isolated buck converter to attenuate output voltage and current ripple. Allowing the output inductor to operate in the discontinuous current mode causes the inverter switches in the isolated buck converter to switch much faster than normal, potentially creating a high current cross-conduction event that can destroy the inverter switches due to excessive current and temperatures.